In recent years, the technology has become available to display varied color frequencies, both in the visual and non-visual ranges, using a variety of light emitting diode (LED) light sources.
For example, U.S. Pat. No. 7,169,995 to Kaun-Chung Lin uses complex digital circuitry to display certain colors based on audio frequencies and volume intensities. This technology requires comparators, analog to digital converters, integrators, a microprocessor and digital LED drive circuits, as well as internal programmed software routines and memory circuits to perform all described functions. The circuit is designed specifically for audio range frequencies. Its digital circuitry inherently produces Radio Frequency Interference. In addition, adding more LEDs requires additional circuitry.
U.S. Pat. No. 7,230,392 to Brett J. Clark describes analog control of light sources, however the capability of the disclosed circuitry is limited. As an example, the Clark device cannot generate maximum brightness from two different groups simultaneously, nor can it be completely dark or create white light. It cannot directly interface with commonly available audio devices. The device uses three LED groups with four LEDs per group. LEDs within two groups are wired in a series/parallel configuration. The maximum current allotment for all three groups is 43 ma. Additional LEDs cannot be added nor can LEDs be removed from the device without adversely impacting the operation of the circuit.
U.S. Pat. No. 7,190,279 to Youssef H. Atris describes a light modulation system for personal or portable electronic apparatuses. It requires the use of multiplexers. LEDs cannot be added to the same channel without adding additional driver circuit components for each additional LED. Its specified design can only provide full brightness for two LEDs.
Accordingly, there is a need for a LED controller that is cost effective, allows more LEDs to be added without additional circuitry, and does not produce Radio Frequency Interference.